| 摘要 |
PURPOSE:To eliminate the variation of the temperature of feed hot water particularly at a small flow speed and a low water quantity by providing delay circuits for keeping combustion for a predetermined period of time when the water temperature at a water temperature sensor part reaches a set value and a burner fire extinguishing signal is output. CONSTITUTION:The control unit comprises delay circuits 34, 44 and 45. The delay circuit 34 detects the trailing edge of an output from a comparator 32, and a high level signal is outputted to a driving part of an electromagnetic valve 31 for a time t0 from the trailing point in time. The delay circuits 44 and 45 detect the trailing edge of an output from a comparator 42, and output high level signals to the drive parts of the electromagnetic valves 31 and 41 for times t1 and t2 from the trailing point in time. When fire is extinguished based on a signal from a thermistor 6, combustion is forcibly prolonged for a longer one of times t0 and t1 in a burner 3, and combustion is forcibly prolonged for a time t2 due to the delay circuit 45 in a burner 4. |
